Open Access Full Text Article Annals of Depression and Anxiety A Austin Publishing Group Research Article Association between Suicidal Behavior and TPH1 and TPH2 Genes of Serotonergic System in Polish Affective Group Joanna Pawlak1*, Monika Dmitrzak-Weglarz1, Aleksandra Szczepankiewicz1,2, Monika Wilkosc3, Abstract Maria Skibinska1, Dorota Zaremba1, Aleksandra Suicide stayed important practical problem in psychiatry. Looking for genetic Rajewska-Rager1,4, Magdalena Labedzka1, Pawel predisposition to suicide we considered polymorphisms of TPH1 and TPH2 Kapelski1 and Joanna Hauser1 genes, a rate limiting enzyme in serotonin synthesis. We focused on affective 1Psychiatric Genetics Unit, Department of Psychiatry, patients, most vulnerable to suicide psychiatric group. In the study were included Poznan University of Medical Sciences, Poland 549 unrelated patients and 370 healthy controls. The selected polymorphisms 2Department of Molecular and Cell Biology, Poznan were genotyped using the Taq Man single-nucleotide polymorphism (SNP) University of Medical Sciences, Poland allelic discrimination method after extracting the DNA from blood sample. The 3Department of Individual Differences, University of Pearson’s chi-square (χ2) test and Fisher’s exact test were applied to test the Bydgoszcz, Poland genotypic and allelic associations. The results were divergent with respect to 4Department of Adult Psychiatry, Poznan University of the diagnosis and suicidal behavior. TPH1 gene polymorphisms rs1800532 and Medical Sciences, Poland rs1799913 revealed an association to diagnosis in group of male BP and MDD *Corresponding author: Joanna Pawlak, Laboratory patients. Also rs7933505 was associated to the diagnosis of BP type I in males. of Psychiatric Genetics, Department of Psychiatry, TPH2 polymorphisms rs1386483 and rs4448731 turn out be associated to BP University of Medical Sciences, ul. Szpitalna 27/33, 60- type II. There were genotypic associations to suicide attempts in four TPH1 SNPs 572 Poznan, Poland, Tel: +48 61 8491311; Fax: +48 61 (rs1800532, rs1799913, rs7933505, rs684302) in male group, but we found no 8480392; Email: [email protected] statistically significant associations between TPH2 polymorphisms and suicidal attempts. Our results partly confirm the role of serotonergic neurotransmission Received: August 08, 2014; Accepted: September 02, in predisposition to suicide and bipolar disorder. The serotonergic system plays 2014; Published: September 05, 2014 a great role in behavior regulation and our results support that the role may partly differ according to sex. Keywords: Suicide; Affective disorder; TPH Introduction hippocampus, hypothalamus and amygdala [11]. A second TPH form (TPH-2) is mainly expressed in the raphe nuclei and to a lesser Serotonin is the neurotransmitter involved in such brain functions extent in the cortex, thalamus, hippocampus, hypothalamus and as mood regulation, aggressiveness, anxiety, sex, sleeping, cognition, amygdala. A significant difference in gene expression with higher memory and learning [1]. It plays important role in inhibition TPH-1 than TPH-2 mRNA levels has been shown in the amygdala of behavior undertaken upon an impulse. Reduced serotonergic and hypothalamus, which are relevant brain areas in BP [12]. releasing into synaptic cleft in the ventral prefrontal cortex may result in weaker inhibition of acting on powerful emotions [2,3]. The role of Aim of the study was to investigate the possible association serotonergic system in etiopathogenesis of depression was postulated between suicidal behavior and selected genetic polymorphisms 40 years ago by Lapin and Oxenkrug [4] and is now very widely in a sample of patients with diagnosis of affective disorders. In the documented [5]. Moreover serotonin is main neurotransmitter present paper we analyzed intronic SNPs within the TPH1 and TPH2 associated with suicidal behavior [6-8]. Epidemiological studies have genes. It was shown that an intronic TPH2 SNP was related to gene demonstrated that suicidal behavior is, at least partially, genetically expression levels [13], so potentially may influence serotonergic determined with a pattern of transmission independent of psychiatric neurotransmission. disorders [9]. Material and Methods Serotonin (5-hydroxytryptamine, 5-HT) elicits a wide array Subjects of physiological effects by binding to several receptor subtypes, In the study were included 549 unrelated patients with bipolar including the 5-HT2 family of seven-transmembrane-spanning, affective disorder (BP) and Major Depression (MDD) (328 female, 221 G-protein-coupled receptors, which activate phospholipase C and male), aged 18-84 (mean=47.04, SD±13.97). Patients were recruited D signaling pathways. TPH is a member of the aromatic amino acid in mental health center of Department of Psychiatry and hospitalized hydroxylase family. The enzyme catalyzes the first and rate limiting at inpatient clinic, Department of Adults Psychiatry, University of step in the biosynthesis of serotonin. There are two isoforms of the Medical Sciences, Poznan. Consensus diagnosis was established by TPH, which are coding by different genes: TPH1 (11p15.3–p14) two psychiatrists using Structured Clinical Interview for DSM-IV Axis and TPH2 (12q21.1). Both isoforms are expressed in human brain I Disorders (SCID-I) [14]. Among patients 216 persons (142 females [10]. TPH-1 is expressed in such regions as frontal cortex, thalamus, and 74 males; 147 BPI, 48 BPII and 21 MDD; see supplementary Ann Depress Anxiety - Volume 1 Issue 3 - 2014 Citation: Pawlak J, Dmitrzak-Weglarz M, Szczepankiewicz A, Wilkosc M, Skibinska M, et al. Association between ISSN : 2381-8883 | www.austinpublishinggroup.com Suicidal Behavior and TPH1 and TPH2 Genes of Serotonergic System in Polish Affective Group. Ann Depress Pawlak et al. © All rights are reserved Anxiety. 2014;1(3): 1014. Joanna Pawlak Austin Publishing Group table) had a suicide attempt in lifetime history. We excluded patients, Quanto. As regards association with the diagnosis the following who committed suicide during clinical observation period, to avoid groups: BP+MDD, BPI, BPII and MDD were compared to controls. phenotypic heterogeneity. The control group consisted of 370 subjects As regards association with the suicide behavior were compared (183 female, 187 male), aged 19-64 (mean=35.37, SD±12.24). We attempters to controls and also compared suicide attempters and non used Polish version of Mini International Neuropsychiatric Interview attempters (accordingly to suggestions of [17]). screen to exclude mental diseases in controls [15]. Attempted suicide Results was defined as self-destructive behavior with at least some intentions to end one’s life [16]. The distributions of genotypes for all analyzed polymorphisms were in Hardy–Weinberg equilibrium in patients as well as in healthy After a detailed description of study procedures informed written controls (p>0.05). Using the Bonferroni correction the significance consent was obtained from all subjects. The protocol of the study was cut-off at p<0.01 was established. approved by the Ethics Committee, Poznan University of Medical Sciences. We found genotypic association between TPH1 rs1800532 and rs1799913 polymorphisms and diagnosis of affective disorder in male Genotyping group. In pure BP type I group rs1800532, rs1799913 and rs7933505 The included polymorphisms fulfilled the following criteria: Minor genotypes were associated to the diagnosis in males. No significant Allele Frequency (MAF) above 0.10 and genotypic correlation (ρ) associations were found in BPII and MDD groups. across the genotypes of maximal 0.85. DNA was extracted from blood samples using the salting out protocol. The selected polymorphisms Among TPH2 polymorphisms we found genotypic association were genotyped using the TaqMan Single-Nucleotide Polymorphism between rs1386483 and rs4448731 and diagnosis of BP type II in (SNP) allelic discrimination method with the ABI 7900HT system. whole group. Association between rs4448731 and BPII was confirmed In the Real-Time PCR reaction the commercially available TaqMan in male subgroup. Genotyping assays (Applied Bio systems, Foster City, CA) were used. In terms of allelic associations we found differences in rs1800532 Gene variants included in the study are depicted in Table1. and rs1799913 polymorphisms between male affective patients and Computations controls. In both SNPs G allele was significantly more frequent in Statistical analyses were performed using Statistical 8.0 package patients (rs1800532: p=0.0049, OR: 0.6463, CI: 0.4789-0.8722 and (STATSOFT, Poland). The concordance of genotypes with Hardy- rs1799913: p=0.0049, OR: 0.6463, CI: 0.4789-0.8722). There were no Weinberg equilibrium was assessed using “Utility Programs for other significant allelic associations to the diagnosis. Analysis of Genetic Linkage”. The Pearson’s chi-square (χ2) test and Significant associations between diagnosis of affective disorder Fisher’s exact test were applied to test differences in the genotypic and genotype are shown in Table 2. and allelic (respectively) distribution between groups of patients and controls. Graph Pad software was used to calculate odds ratios Then the association between suicide attempts and genotype (OR) for the alleles. Power analysis was performed using Program was investigated. We found an association between TPH1 rs684302 polymorphism and suicidal attempts in comparison of suicide Supplementary Table: Gender, diagnosis and suicide attempters’